PVC is rigid. Your chances finding something with the exact spacing is pretty slim. I'd ask Chad for the center-to-center spacing on the atomizer
threads. With that and measuring the diameters of your atomizers you'd know what you're looking for. I also believe that the barrel diameter on different atomizers is different. Even from one type of 510 to another so it would have to have some sort of rubber grommet or something.
A hybrid solution with a hard and soft material solution might be a lot better. Maybe a rigid "Y" like the one pointed to above mated to short pieces of silicon tubing that would in turn mate to the atomizers. In that case you would want the "Y" piece tubing to have a diameter to fit inside the silicon tube "couplers" -- roughly the same size as an atomizer barrel. Choose the diameter of the smallest atomizer barrel you are considering. Relatively thick walled silicon tubing would give you couplers with some rigidity while still able to "stretch" over larger diameter atomizers. The coupler tubing pieces would probably need to be about 1" or longer to have enough to fit over the "Y" ends and have enough to accomodate the stretch over larger atomizers and compensate for a center-to-center measurement on the "Y" piece that is a bit different from the center-to-center measurement between the atomizers. P.S. silicon won't melt or warp with the heat from a hot atomizer barrel.
note: my 901 appears to have a barrel diameter of approximately 3/8"
KR808D seems to be the same.
LR 510 appears to be a bit less than 1mm smaller?
and a regular 510 about 1mm smaller?
801s naturally are huge.
How's that for an idea?